Congratulations! <~ on getting married, not for posting...
I would stray from the 16-50, as I think there isn't as much of difference from the kit lens as you would think for the price, unless you NEED 16-50mm @ 2.8
If that was the case I would say to go with the TAMRON 17-50 F2.8, no chance of SDM failure
I would lend it to you but just sold it recently.
By your choices, I would say the 21mm, the smaller the form factor, the easier it will be to carry and the more pictures you will take.
I had the 35LTD, sorry to say I was not impressed, I tested it side by side with the DA(L) 35mm 2.4 and ended up trading the 35LTD away.
For the night shots, bring a small tripod, it doesn't need to be big or too sturdy with the K-X and a pancake lens.
Make sure to bring back some nice shots for us. Best of luck!